“Well, that’s a perfectly ordinary sound for a tree to make,” Bambleby called. “Nothing at all to worry about.”

“Have you ever considered,” I said, removing my measuring tape from my bag, “that I might be more capable than you think? I have written dozens of papers, read hundreds of analyses. I’ve also had numerous firsthand dealings with the Folk, from hobs to bogles to an extremely self-entitled aristocrat.”

“I don’t doubt that most of your success to date is the result of cleverness. But have you ever considered how much you owe to luck?”

My hand clenched. I finished the measurements without replying—base and canopy. Then I withdrew my field book and began taking notes. I scraped at the snow and found, trapped beneath it, a thin carpet of leaves. As I worked, Bambleby’s grumbling and stomping reached a volume one normally associates with teams of horses.

“If you would only tell me what you’re so worried about,” I said calmly. If I am being honest, I was rather enjoying myself.

“I can’t,” he said through his teeth.

“Can’t or won’t?”

“I literally and physically cannot tell you.”

“Stop being dramatic.”

“I am not,” he said, with the most dramatic groan I have heard him utter. Shadow seemed to take inspiration from his histrionics and whined louder.

I turned back to the tree. I could almost hear him stewing. Well, let him. I fetched a pair of metal tweezers from my pack and carefully plucked a leaf from the frost. It was lovely, segmented like a maple and white as the trunk and boughs, though it also had a coating of short white hairs, like some sort of beast. I placed the leaf within a small metal box I habitually use to collect such samples, many of which have found their place in the Museum of Dryadology and Ethnofolklore at Cambridge. Unfortunately, the wind chose that moment to stir the leaves I had uncovered. I leapt aside as quickly as I was able, but one of them brushed my bare fingertips. I felt a shock of cold, as if I had plunged my hand into ice melt.

“Dammit,” I muttered. I pressed the coin to my hand immediately, and the pain lessened.

“What?” Bambleby said. His hearing is inconveniently sharp.

“Nothing. I thought you’d gone, but then I saw that you hadn’t.”

“That’s it,” he said. “Shadow, go and collect your suicidal mistress.”

I laughed. “Shadow only responds to me. You think—”

Shadow burst from the trees and leapt upon me. I fell into a snowbank, and before I even knew what was happening, he had grabbed my cloak in his teeth and was dragging me.

“Shadow!”

The dog seemed not to hear my shrieks. I slid over snow and roots, and my backside barked painfully against a rock. The land sloped a little towards the river, and with one final tug, Shadow slid me the rest of the way like an ungainly sledge to land in a heap at Bambleby’s feet.

I gathered myself, panting. “Shadow!” I snapped, full of fury and betrayal, and he hung his head low, that terrible doggish guilt in every line of his body. But he did not move from his position between me and the tree.

“Good boy.” Bambleby seized my hand and dragged me along the riverbank. Oh, I was going to kill him. I wrenched him so hard that he stumbled but did not fall, catching himself with that infuriating grace that he often tries to conceal. I yanked him again so that we were facing each other and grabbed his other arm, the better to shove him into the river. His green eyes widened with outrage when he realized what I was intending, his golden hair falling into them—horrendously unfair that he should look beautiful even when he’s angry, instead of going blotchy and beady-eyed like a normal person. If I hadn’t been decided on sending him into the river before, I was now.

That was when the land broke open, showering us in snow and dirt. Roots wormed their way out from the soil, white and smooth as bone. They twined themselves around Bambleby and yanked him onto his back, then dragged him towards the white tree in an uncanny mirror of what I had undergone.

“Wendell!” I lunged forward, trying to wrench the roots away from him. They showed no interest whatsoever in me, nor Shadow, who pounced and worried at them until they fell away. But more rose to take their place.

“Why does it want you?” I cried.

“Why do you think, you cold-blooded lunatic of a woman?” he yelled, clawing at the ground. This was followed by a series of curses in what I assumed to be Irish.

I stabbed at the roots with my pocketknife. At the same moment, though, my mind was racing through stories, texts, journals. “Can you not—can you not say it?”

He gave me one of his impossibly green glares. We were nearing the base of the tree, where a hollow like a mouth had yawned open, black and writhing with roots like white worms. “No!”

“Oh,” I breathed. My pocketknife was having little effect, but I kept up the stabbing nevertheless—I believe I stabbed him once, accidentally, for I had gone back into my mind. “You can’t reveal to me that you’re Folk—it must have been part of the enchantment that exiled you from your world. Isn’t that it? I’ve heard of that—yes, that account of the Gallic changeling. And isn’t it a peripheral motif within the Ulster Cycle?[*] Bryston’s theory was that—”

“Oh, God,” he moaned. “She wants to discuss theory at a moment like this. I am doomed, aren’t I?”

The roots were pulling him deeper. I grabbed at his shoulders and yanked, but I only slipped in the snow and thumped onto my side. Shadow gripped Bambleby’s sleeve with his teeth and put his own back into it. Neither of us had the slightest effect.

“Well, what do you want me to do?” I cried. “I know what you are, Wendell—I said it, so you needn’t reveal yourself! Can’t you use your magic now? Can I help you?”

“Yes, you can stop pontificating at me for half a second so that I can concentrate,” he yelled over the lashing roots. “I haven’t done this in a very long time. I don’t even know if I remember how. And if you would please encourage your fanged familiar to stop mauling my cloak!”

I drew Shadow back. It took all of my strength, for he kept howling and lunging at Bambleby’s disappearing body. I don’t know what I expected him to do, but something loud and impressive, certainly. What actually happened was both underwhelming and utterly terrifying: he folded himself into the earth and was gone. I have seen brownies and trows do this, of course, but they are brownies and trows, creatures of leaf and moss; they are not Wendell. And then he did worse than that, stepping out of a tree on the other side of the river, creating a horrible confusion within me as my mind tried to convince my eyes that he had come from behind the tree, but of course he had not.

Shadow grabbed at my cloak and started pulling again, but I was already running, and so we ran across the mostly frozen river like a bride from a nightmare, her train supported by a servant. The ice cracked near the far bank but did not break, and Bambleby grabbed me before I fell.

He tried to pull me on, but I dug in my heels and turned to watch the spectacle unfolding on the opposite shore. The white tree itself was still, dreamlike, while beneath it the roots writhed with impotent rage. The river ran too deep; they could not burrow beneath it.

“I want a piece of the bark,” I said suddenly.

He gave me such a look of disbelief that I pressed on, “For the paper! We need illustrations, Wendell. Exhibits. How else do you expect people to understand—”

“We can go back there, and you can watch that thing crack my skull open and fill it with monstrosities,” he said. “Perhaps I’ll sit for an illustration after—what do you think?”

“If I went alone, given that it paid me no mind before—”

He took me by the shoulders and shook me. “What is the matter with you? You are many things, which I will be happy to enumerate later, but obtuse is not one of them.”